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Scala Reflection Library 2.13.2 - scala.reflect.api.Trees.TreeApi

EXPERIMENTAL

This trait defines the node types used in Scala abstract syntax trees (AST) and operations on them.

Trees are the basis for Scala's abstract syntax that is used to represent programs. They are also called abstract syntax trees and commonly abbreviated as ASTs.

In Scala reflection, APIs that produce or use Trees are:

• Annotations which use trees to represent their arguments, exposed in Annotation.scalaArgs.
• reify, a special method on scala.reflect.api.Universe that takes an expression and returns an AST which represents the expression.
• Macros and runtime compilation with toolboxes which both use trees as their program representation medium.

Trees are immutable, except for three fields pos, symbol, and tpe, which are assigned when a tree is typechecked to attribute it with the information gathered by the typechecker.

The following creates an AST representing a literal 5 in Scala source code:

Literal(Constant(5))

The following creates an AST representing print("Hello World"):

Apply(Select(Select(This(TypeName("scala")), TermName("Predef")), TermName("print")), List(Literal(Constant("Hello World"))))

The following creates an AST from a literal 5, and then uses showRaw to print it in a readable format.

import scala.reflect.runtime.universe.{ reify, showRaw }
print( showRaw( reify{5}.tree ) )` // prints Literal(Constant(5))

For more information about Trees, see the Reflection Guide: Symbols, Trees, Types.

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